CVS shares fell 16% in pre-market trading on Tuesday after the company lowered its outlook for profits this year.

"Very recent pharmacy network changes in the marketplace are expected to cause some retail prescriptions to begin migrating out of our pharmacies this quarter," said CEO Larry Merlo in the earnings statement.

"In addition, we are currently experiencing slowing prescription growth in the overall market as well as a soft seasonal business. These factors combined are leading us to reduce the mid-point of our guidance for this year by five cents per share."

In a statement, CVS said it expected full-year adjusted earnings per share between $5.77-$5.83, down from a previously announced range of $5.81-$5.89, and below analysts' estimate for $5.85.

For the third quarter, CVS reported net revenue of $44.6 billion, below the forecast for $45.3 billion according to Bloomberg.

The stock lost 15% this year through the market close on Monday. Markets Insider